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Friday, July 5, 2013

Fireworks Smoke: Air Quality Alert

Well, it was not quite as bad as Beijing during the winter, but air quality really degraded around the Northwest last night as massive amounts of fireworks were deployed.

A number of air quality sites measured values of small particulates at unhealthy levels, particularly for those vulnerable to their effects (asthmatics, those with heart or lung disease, etc.). I was standing along the shores of Lake Washington last night and a smoky, sulfurous miasma was evident, both from commercial fireworks and from the numerous individual displays. (And this is with fireworks being ILLEGAL in much of the area!!) I believe this was a particularly bad air quality year from fireworks, for reasons I will explain.

Let's check the numbers, provided the Puget Sound Clean Air Agency, a really excellent organization that works to keep our air breathable. I will be showing you concentrations of small particles (PM2.5, less than or equal to 2.5 microns in size, particles that can make their way deep into your lungs and cause all kinds of problems).

First, Seattle in the Duwamish Valley. Big spike from a background level of roughly 10 (micrograms per cubic meter) to 60, getting well into the range of being unhealthy for sensitive groups. (click on this or subsequent figures to enlarge).

Lynnwood was MUCH worse, spiking well into the UNHEALTHY levels for everyone (about 120). The red line shows preceding 24-h averages.

Even a relatively small town, like Aberdeen, WA seems to have lots of firework smoke, with levels getting well into the unhealthy range (about 90).

Similar values were noted in suburban North Seattle at Lake Forest Park.

But if you want to find REALLY bad air...getting close to Beijing levels...head to the Tacoma Tideflats where a startling peak of about 275 was observed. Folks...this is really bad for you.

I haven't done a study of the levels each year, but if my memory serves me correctly these levels were higher than most previous years....something confirmed by an air quality scientist at Puget Sound Clean Air Agency. Why?

First, the winds were relatively light last night...as suggested by the following wind plot for 10 PM July 4. Circles with no wind barb indicate calm winds. A bard with a single small line indicates only a few knots. Low winds mean less turbulence and vertical mixing. Thus, less clean air being mixed down and less dispersion of the smoke.

Second, the vertical structure of the atmosphere was relatively stable (little mixing), with a stable layer (in this case one with temperature staying the same with height) from from roughly 925 hPa (about 2500 ft) to 850 hPa (around 5000 ft). Below is a vertical sounding at Quillayute on the Washington coast, provide temperature (right line) and dew point (left line) with height. The stable layer would act as a cap to keep pollutants in.

Air quality should improve today, although I suspect there will be some more fireworks tonight, which will keep the levels above background.

2 comments:

Have you considered that a lot of particulates would have been generated by the smoke from thousands of barbecues? I think one or two hours of barbecuing per grill could have contributed about as much particulate pollution as a few minutes of fireworks.

It did seem a bit smokier and hazier than normal for the 4th of July. At least up on Capitol Hill. I noticed this on the walk home after watch the show. Even on the far (east) side of the hill my eyes were burning. It reminded me of smoggy days in Southern California. I assumed it was from a combination of smoke from fireworks and the nearby marina fire (of which I did not know of at the time).